Punch holder shank



Patented May 5, 1942 UNETED STA'itlfi QFFICE PUNCH HOLDER Emil A. Baumbach, River Forest, 111. Application April 21, 194 1, Serial No. 389,574

2 Claims.

My invention relates to punch holder shanks.

One of the objects of my invention is to provide a punch holder having guide openings for cooperating with the leader pins and having a shank by means of which the punch holder may be secured to the reciprocating head secured to the punch holder in such a way that the punch holder cannot rotate with respect to the shank.

A further object of my invention is to provide such a construction which will be durable, inexpensive to manufacture and neat in appearance.

Further objects and advantages of the invention will be apparent from the description and claims.

In the drawing, in which my invention is illustrated:

Figure l is an elevational view of a die set, parts being broken away;

Fig. 2 is an enlarged sectional view on the line 2-2 of Fig. 1;

Fig. 3 is a greatly enlarged sectional view on the line 33 of Fig. 2; and

Fig. 4 is a perspective view of a retaining key.

Referring to the drawing in detail, the construction shown comprises a die shoe I, leader pins 2 secured to the die shoe, and a punch holder 3 having leader pin bushings-4 for alignment with the leader pins 2 and having a shank 5 for securing the punch holder in position in the reciprocating head. The die shoe and leader pins may be of any usual or suitable construction. The punch holder comprises a plate of substantially uniform thickness, the upper and lower faces of which may be machined. The shank 5 has an enlarged portion 6 to be secured to the reciprocating head and a reduced externally threaded extension I screwed into an internally screw-threaded opening in the punch holder. This extension I is screwed into the punch holder until the machine finished shoulder 8 at the upper end of the threaded extension snugly engages the finished upper surface of the punch holder.

In order to insure that the shank 5 has no turning or twisting movement with respect to the holder 3, the reduced screw-threaded extension l' is provided with a keyway 9 which may be milled therein and a tapered key H1 is driven solidly into this keyway and the end of the key is then cut off and may be machined so as to be flush with the lower face of the holder plate. The keyway 9 is cut so as to have a slight flare downwardly, and the key itself is machined so that it will taper upwardly slightly. The upper end of the keyway is curved as shown at H, so that when the upper end of the wedge begins to engage the curved portion of the keyway, the upper end of the key will be forced slightly inwardly so that the key will bear most forcibly at the points A and B of the keyway, as shown in Fig. 3.

The edge of the key next to the internal threads in the opening is provided with a knife edge 12 for cutting into and mutilating the internal threads I3 as the key is driven into place. As the key first begins to enter the keyway, the knife edge of the key will barely touch the internal threads, but as the key is driven in, the sloping engaging surfaces of the ,key and keyway will force the key to the left, as viewed in Figs. 1, 2, and 3, and will cause the knife edge to bite into the threads, mutilating the threads and preventing any possible twisting or turning movement of the punch holder 3 with respect to the shank 5. The engagement of the inner end of the key with the curved portion of the keyway and its travel along this keyway for a short distance causes the inner end of the key to bite deeply into the threads and prevent any possibility of the key being dislodged from the keyway.

In order to insure that the finished annular shoulder on the shank will snugly engage the finished upper surface of the punch holder when the shank is being screwed into the holder, the upper end of the threaded extension is provided with an annular recess or depression 14 of smaller diameter than the inside diameter of the threads of the opening, as shown in Fig. 3.

It will be seen that when the key is driven into place, as shown in Fig. 3, the threads will be mutilated to such an extent that it will be practically impossible for any jarring or vibration to loosen the key, thus insuring that the punch holder cannot rotate with respect to the shank and holding the guide bushings in proper alignment with respect to the leader pins.

Further modifications will be apparent to those skilled in the art and it is desired, therefore, that the invention be limited only by the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A punch holder construction comprising a metal plate having a fiat, machined, upper face, leader pin openings therethrough for alignment with leader pins, said construction comprising also a shank fastened to said plate for securing the punch holder in position, said plate having a screw-threaded opening therethrough, said shank having a reduced threaded extension screwed into said threaded opening and having a machined shoulder adjacent the upper end of said threaded extension snugly engaging the machined upper face of said plate, said extension having a longitudinally extending keyway in its side and a key driven into said keyway, said key having an edge portion engageable with the threads of the threaded opening for mutilating them as the key is driven into the keyway, said punch holder construction being provided with an annular recess adjacent said machined shoulder to provide clearance for the threads adjacent the shoulder.

2. A punch holder comprising a metal plate having a fiat, machined, upper face, leader pin openings therethrough for alignment with leader pins, and a shank fastened to said plate for securing the punch holder in position, said plate having a screw-threaded opening therethrough, said shank having a reduced threaded extension screwed into said threaded opening and having a machined shoulder adjacent the upper end of said threaded extension snugly engaging the machined upper face of said plate, said extension having a longitudinally extending keyway in its side and a key driven into said keyway, said key having an edge portion engageable with the threads of the threaded opening for mutilating them as the key is driven into the keyway, said extension having a reduced annular recess adjacent said machined shoulder of smaller diameter than the diameter of the root of the thread.

EMIL A. BAUMBACH. 

